Synthetic surfactant-free finish, sheet having synthetic surfactant-free finish, articles having sheet with synthetic surfactant-free finish, and related methods

ABSTRACT

Nonwoven (and film) topsheet and acquisition/distribution materials treated with a hydrophilic, synthetic surfactant-free finish, absorbent articles for infant or incontinence care that contain these materials, and methods for apply such finishes and/or making such absorbent articles.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/079,879, filed Nov. 14, 2014, which is incorporated by referencein its entirety.

FIELD OF INVENTION

The present invention relates generally to disposable absorbent productssuch as infant diapers, adult incontinence briefs, pull-up underwear,bladder control pads, bedpads; and, more particularly, but not by oflimitation, to nonwoven topsheet and acquisition/distribution layers(ADL's) finished with durable, hydrophilic, synthetic surfactant-freefinishes, and to absorbent products that contain topsheets and ADL'streated with a synthetic surfactant-free finish. The present syntheticsurfactant free-finishes, and the methods of applying it, can also beuseful for woven materials comprising hydrophobic fibers that require ahydrophilic finish.

BACKGROUND

Absorbent articles, such as baby diapers, training pants, adultincontinence products and other such absorbent products include atopsheet that is closest to the wearer, an outer, moisture-impermeablebacksheet, and an absorbent core. Disposable absorbent products have metwith widespread acceptance in the marketplace for a variety ofapplications, including infant and adult incontinence care, in view ofthe manner in which such products can provide effective and convenientliquid absorption and retention while maintaining the comfort of thewearer. However, experience has shown that a need exists for moreskin-friendly topsheet nonwovens. Examples of absorbent articleconstructions with which the present sheets can be used are disclosed inUnited States Patent Application Publications No. US 2006/0178650 andNo. US 2010/0280479.

The nondurable, or fugitive, nature of synthetic surfactants used on allpolyolefin topsheets and acquisition/distribution layers in use todayplay a role in absorbent product acquisition and rewet performance, buthave a potential to compromise skin health. Synthetic surfactants areused as penetration aids in transdermal drug delivery. Syntheticsurfactants washed from the nonwoven fibers during product use canincrease the permeability of stratum corneum to all potential irritants,including the synthetic surfactant itself. Various emollient materialshave be used in an attempt to restore barrier function to damaged skin,but a straightforward solution to the problem is to eliminate allsynthetic surfactant from the nonwoven. In this invention we haveidentified potential chemistries for imparting wettability to polyolefinnonwovens and films, and teach how they can be appliedeffectively—without the use of any conventional synthetic surfactantsand with the goal of promoting skin health.

Nonwovens made from polypropylene are hydrophobic. By application ofsuitable finishing treatments, it is possible to impart semi-durablehydrophilic properties to the nonwoven to achieve performance in liquidstrike-through and liquid runoff that is required for their use inabsorbent products. Suitable finishing treatments are typicallyproprietary blends of synthetic surfactant solutions which arecommercially available, for example, from Schill & Seilacher AG (e.g.Silastol PHP 26, Silastol PHP 90, & Silastol 163), and Pulcra Chemicals(e.g. Stantex S 6327, Stantex S 6087-4, & Stantex PP 602). They aretypically applied to spunbond nonwovens in the range of 0.004-0.006 gmsolids/gm nonwoven (i.e. 0.4-0.6% wt/wt). An example of a syntheticsurfactant that has been used widely used in commercially-availabletopsheet finishes would be Triton GR-5M, an anionic sulfosuccinatesurfactant manufactured by Dow Chemical Company. Other types ofsurfactants used are based on fatty acid polyethylene glycol esters.

U.S. Pat. Nos. 5,938,649 and 5,944,705, Ducker, et al., disclosed anabsorbent article containing aloe vera on the surface of the articlecontacting the wearer's skin to reduce rash. A preferred embodiment ofthis invention was an essentially water-free aloe vera in a waterlesslubricant that was applied to an absorbent product independently of anysurfactant finish on the topsheet nonwoven. Procter & Gamblecommercialized a baby diaper in the late 1990's/early 2000's thatcontained an emollient lotion, applied in stripes, on a conventionaltopsheet nonwoven. U.S. Pat. No. 6,459,014 B1, Chmielewski and Erdman,mentions pH control agents such as citric acid and sodium citrate thatcan be added to a nonwoven topsheet in conjunction with an optionalsurfactant. However, all examples in this patent included syntheticsurfactant and there was no discussion of how a nonwoven could besuccessfully treated with a surfactant-free solution of citric acid, orwhether it could impart useful hydrophilic properties to the nonwoven.Furthermore, citric acid and sodium citrate are freely soluble in salinesolution and would not provide a sufficiently durable finish to atopsheet nonwoven. More recently, in U.S. Pat. No. 6,936,345 B2, Wildet. al. describe a process for finishing nonwovens in such a way to meetrequirements in regard to the permanence of the hydrophilic finish andbe capable of providing an additional benefit, in this case suppressionof the growth of bacteria. They described an aqueous antimicrobialfinish containing a monoester of glycerol, a fatty acid and chitosan.The monoester of glycerol and the fatty acid are surface activeingredients that facilitate spreading of the antimicrobial finish on thenonwoven in the finishing process.

Salas, et al. in “Water-Wettable Polypropylene Fibers by Facile SurfaceTreatment Based on Soy Proteins”, ACS Appl. Mater. Interfaces 2013, 5,6541-6548, reported on the modification of the wetting behavior ofpolypropylene nonwovens after adsorption of soybean proteins. UsingQuartz Crystal Microgravimetry with thin, flat films of polypropylene,they confirmed a high affinity of adsorption for soy protein onpolypropylene. A fast initial adsorption occurred in the order ofseconds. This showed that adsorption of soy protein will indeed occur onpolypropylene if the protein solution is forced to be in contact withthe polymer surface. When extending their work to a polypropylenenonwoven, they noted that the hydrophobic nonwoven floated on thesurface of the protein solution and prevented effective adsorption ofthe protein. To overcome this issue, they first immersed thepolypropylene nonwovens in 2-propanol to clean the nonwoven, followed byan immersion into 1 mg/mL 2-propanol solution of cationicdioctadecyldimethylammonium bromide surfactant.

SUMMARY

A novel nonwoven or film topsheet or other acquisition/distributionmaterials that has a hydrophilic, synthetic surfactant-free finish thatis useful for absorbent products for infant or incontinence care thatcontain these materials. These materials are made by intimately treatingthe raw unfinished materials in the absence of air bubbles with anaqueous solution of a hydrophilic, synthetic surfactant-free finish andthen drying the materials.

Some embodiments of the present hydrophilic, synthetic sheets comprise:a sheet of synthetic material having a first surface; where the sheetcomprises a hydrophilic finish including molecules of a water-solubleproteins dispersed on the first surface; and where the finish issubstantially free of synthetic surfactants. In some embodiments, thefinish does not include synthetic materials capable of reducing thesurface tension of water below 50 milliNewtons/m (mN/m). In someembodiments, the sheet comprises a nonwoven fabric or a film. In someembodiments, the sheet is a topsheet of an absorbent article. In someembodiments, the sheet is a distribution-acquisition layer of anabsorbent article. In some embodiments, the water-soluble proteincomprises a thermally-denatured protein. In some embodiments, a 0.4-1.2%aqueous solution of the water-soluble protein has a surface tensiongreater than 50 milliNewtons per meter (mN/m). In some embodiments, a1.2-10% aqueous solution of the water-soluble protein has a surfacetension greater than 50 milliNewtons per meter (mN/m). In someembodiments, at least 0.004 grams of the molecules of the water-solubleprotein are dispersed on the sheet for each gram of sheet.

Some embodiments of the present disposable absorbent articles comprises;a topsheet comprising an embodiment of the present hydrophilic,synthetic sheets; a backsheet; and an absorbent core disposed betweenthe topsheet and the backsheet.

Some embodiments of the present disposable absorbent articles comprise;a topsheet; a distribution-acquisition layer comprising an embodiment ofthe present hydrophilic, synthetic sheets; a backsheet; and an absorbentcore disposed between the distribution-acquisition layer and thebacksheet.

Some embodiments of the present methods (e.g., of imparting hydrophilicproperties to a sheet of polymeric material) comprise: applying anaqueous solution of a water-soluble protein to a sheet of polymericmaterial in an aqueous solution; and drying the sheet such that at leasta portion of the protein is retained on a surface of the sheet; wherethe aqueous solution is substantially free of synthetic surfactants. Insome embodiments, at least a portion of the water-soluble protein isthermally-denatured. In some embodiments, the sheet comprises a nonwovenfabric or a film.

Some embodiments of the present methods further comprise, prior toapplying the aqueous solution to the sheet: admixing the water-solubleprotein in water; heating the water to a temperature of between 40°Celsius (C) and 99° C.; and stirring the admixture to dissolve theprotein in the water. In some embodiments, the water is heated beforeadmixing the water-soluble protein. In some embodiments, the temperatureof the water is maintained between 40° C. and 99° C. during at least aportion of the stirring. In some embodiments, the temperature of thewater is maintained between 40° C. and 99° C. for a period of timesufficient to thermally denature at least a portion of the protein. Someembodiments further comprise: adjusting the pH of the admixture of waterand protein prior to heating the temperature of the admixture.

In some embodiments of the present methods, the temperature of thesolution is between 20° C. and 40° C. during at least a portion ofapplying the aqueous solution to the sheet.

In some embodiments of the present methods, applying the aqueoussolution to the sheet comprises: immersing the sheet a first time in thesolution; and immersing the sheet a second time in the solution. Someembodiments further comprise: calendaring the sheet between immersingthe sheet the first time and immersing the sheet the second time.

In some embodiments of the present methods, applying the aqueoussolution to the sheet is performed with at least one coating apparatusselected from the group consisting of: a slot die, a knife coater, akiss coater, a gravure printer, a multiple-roller coating apparatus, anda screen coating apparatus.

In some embodiments of the present methods, the aqueous solutioncomprises a preservative. In some embodiments, the preservativecomprises one or more preservatives selected from the group consistingof: Plantservative, MicroSilver, and Nutrabiol.

In some embodiments of the present methods, the protein comprises soyprotein isolate (SPI).

Some embodiments of the present finishes (e.g., for a synthetic nonwovenor film) comprise: an aqueous solution of a water-soluble,thermally-denatured protein, the solution having a surface tensiongreater than 50 milliNewtons per meter (mN/m). In some embodiments, theaqueous solution comprises a preservative. In some embodiments, thepreservative comprises one or more preservatives selected from the groupconsisting of: Plantservative, MicroSilver, and Nutrabiol.

The term “coupled” is defined as connected, although not necessarilydirectly, and not necessarily mechanically; two items that are “coupled”may be unitary with each other. The terms “a” and “an” are defined asone or more unless this disclosure explicitly requires otherwise. Theterm “substantially” is defined as largely but not necessarily whollywhat is specified (and includes what is specified; e.g., substantially90 degrees includes 90 degrees and substantially parallel includesparallel), as understood by a person of ordinary skill in the art. Inany disclosed embodiment, the terms “substantially,” “approximately,”and “about” may be substituted with “within [a percentage] of” what isspecified, where the percentage includes 0.1, 1, 5, and 10 percent.

The terms “absorbent article” and “absorbent garment” are used in thisdisclosure to refer to garments or articles that are configured toabsorb and contain exudates and, more specifically, refer to garments orarticles that are placed against or in proximity to the body of a wearerto absorb and contain the exudates discharged from the wearer's body.Examples of such absorbent articles or absorbent garments includediapers, training pants, feminine hygiene products, bibs, wounddressing, bed pads, and adult incontinence products. The term“disposable” when used with “absorbent article” or “absorbent garment”refers to garments and articles that are intended to be discarded aftera single use.

“Absorbent core” is used in this disclosure to refer to a structurepositioned between a topsheet and backsheet of an absorbent article forabsorbing and containing liquid received by the absorbent article. Anabsorbent core can comprise one or more substrates, absorbent polymermaterial, adhesives, and/or other materials to bind absorbent materialsin the absorbent core.

A device or system that is configured in a certain way is configured inat least that way, but it can also be configured in other ways thanthose specifically described.

The feature or features of one embodiment may be applied to otherembodiments, even though not described or illustrated, unless expresslyprohibited by this disclosure or the nature of the embodiments.

Some details associated with the embodiments described above and othersare described below.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings illustrate by way of example and not limitation.For the sake of brevity and clarity, every feature of a given structureis not always labeled in every figure in which that structure appears.Identical reference numbers do not necessarily indicate an identicalstructure. Rather, the same reference number may be used to indicate asimilar feature or a feature with similar functionality, as maynon-identical reference numbers.

FIG. 1 depicts a plan view of one example of the present absorbentarticles.

FIG. 2-3 depict tables of various characteristics of the present sheetsand/or finishes.

FIGS. 4-5 depicts absorbance versus the square root of time for rinsetests for one embodiment of the present sheets.

FIG. 6-15 depict tables of various characteristics of the present sheetsand/or finishes.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Referring now to the drawings, and more particularly to FIG. 1, showntherein and designated with the reference numeral 1 is an example of thepresent absorbent articles. In the embodiment shown, article 1 includesa front portion 2, a rear portion 3, a core portion 4, and band portions5. In this embodiment, absorbent article 1 is configured as a diaper; inother embodiments, the present absorbent articles can be configured aspads and/or the like.

In the embodiment shown, front portion 2 includes fasteners 6 (e.g.,adhesive, hook-and-loop patches, or other fastening structure) and bandportions 5 include fasteners 6′ and 7 (e.g., adhesive, hook-and-looppatches, or other fastening structure). In this embodiment, article 1comprises an absorbent core 8 with an outer zone 9 and a middle zone 10.In the embodiment shown, article 1 also comprises a second absorbentcore 12; other embodiments may include only a single absorbent core. Inthis embodiment, article 1 further comprises a distribution-acquisitionlayer 13 that spans at least absorbent core 8 (e.g., and absorbent core12).

In the embodiment shown, article 1 is bounded by a back sheet 18 (thatfaces outward when worn) and a top sheet 19 (that abuts a wearer's skinwhen worn). In this embodiment, top sheet 19 and back sheet 18 areco-extensive and have dimensions larger than those of the absorbentcore. Back sheet 18 typically prevents liquid absorbed and contained inthe absorbent core from wetting articles (e.g., clothing) that contactabsorbent article 1. In many (if not all) embodiments, back sheet 18 isimpervious to liquids and can comprise a thin plastic (e.g.,polyethylene) film, although other flexible liquid impervious materialsmay also be used. In some embodiments, back sheet 18 may be “breathable”or configured to permit vapors to escape from the absorbent core whilepreventing exudates from passing through back sheet 18.

In the depicted embodiment, top sheet 19 is joined with and superimposedon the back sheet 18 thereby forming the periphery of article 1. In someembodiments, top sheet 19 is compliant, soft feeling, and non-irritatingto the wearer's skin. In many (if not all) embodiments, top sheet 19 isliquid pervious permitting liquids to readily penetrate through itsthickness. Top sheet 19 can be manufactured from a wide range ofmaterials such as porous foams, reticulated foams, apertured plasticfilms, natural fibres (e.g., wood or cotton fibres), synthetic fibres(e.g., polyester, polyethen or polypropylene fibres) or from acombination of natural and synthetic fibres. In some embodiments, topsheet 19 includes both hydrophilic and hydrophobic material (e.g.,positioned in different zones to meet different demands, such as, forexample, to isolate a wearer's skin from liquids in the absorbent core).In various embodiments, top sheet 19 may be woven, non-woven, spunbonded, carded, or the like.

In the embodiment shown, fluid acquisition-distribution layer 13 isconfigured to collect and temporarily hold discharged body fluid. Forexample, a portion of discharged fluid may (e.g., depending upon thewearer's position) permeate acquisition-distribution layer 13 and beabsorbed by the absorbent region in the area proximate to the discharge.However, since fluid is often discharged in gushes, the portion of theabsorbent core in such area may not absorb the fluid as quickly as it isdischarged, and the acquisition-distribution layer is configured totransport fluid from the point of initial fluid contact to other partsof the acquisition-distribution layer for absorption by the absorbentcore.

As described below, the present finishes and methods enable themanufacture of synthetic surfactant-free hydrophylic sheets that aresuitable for use as a topsheet (e.g., 19) and/or as anacquisition-distribution layer (e.g., 13) in absorbent articles (e.g.,1). As described in more detail below, the present finishes and methodsinvolve the application of denatured proteins to sheets comprisinghydrophobic material (e.g., films or nonwovens) to impart hydrophilicproperties. In general, the present finishes comprise proteins insolution and the present methods involve applying the solution to asheet to distribute the proteins, and subsequently drying the sheet suchthat the proteins are deposited on the sheet.

I. Solution Properties of Soy Protein Isolate (SPI)

Clarisoy® 100 is a 100% water-soluble soy protein isolate (SPI)commercially available from Archer Daniels Midland (ADM) and BurconNutraScience Corporation. The effects of temperature and pH wereinvestigated on solutions of SPI prepared via a concentrated pre-mix,mix, and cook protocol. Elevated temperatures were used in an attempt toat least partially denature the protein and promote adhesion anddurability to the nonwoven finish. Properties of proteins that promoteadhesion and durability to nonwoven fibers are related to propertiesthat can lead to an undesirable effect of biofouling in medical devicesupon exposure of hydrophobic polymer surfaces to protein solutions.

FIG. 2 shows certain properties of various mixtures made with the SPIand the methods by which those mixtures were made. As shown, SolutionNo. 1 was prepared by first premixing 0.25% solids of SPI in 90° C.distilled water at high shear until the soy powder was uniformlydispersed in the liquid. The solution was then diluted with an equalvolume of 90° C. distilled water and mixed under low shear for about 10minutes. Before the “cook” stage, the pH of the mixture was adjusted topH 8 with 0.1 N NaOH. Following the pH adjustment, the mixture was“cooked” or maintained at an elevated temperature with low-shear mixingfor 60 minutes to simulate use of the mixture in a commercial process.The appearance of this mixture was cloudy at 90° C. After cooling to 22°C., a precipitate settled from the mixture, indicating the presence ofundissolved solids. Formation of a precipitate was associated withadjustment of pH while the dispersion was at an elevated temperature.When solutions are prepared without pH adjustment, the SPI can bedispersed either in water at room or elevated temperature to form clearsolutions. It was also determined that comparable solution propertieswere achieved when the pre-mix was eliminated and the cook time reducedto the time required to bring the solution to temperature (see mixturesNo. 3 and 4). The mixture that formed a precipitate may not be the bestfor obtaining the desired finish on nonwovens. Because of thedifferences in solution properties indicated above, the investigation ofthe ability of SPI to impart a hydrophilic finish to nonwovens wasfocused on solutions mixed at elevated temperature both with and withoutprior modification of solution pH. In experiments in which pH wasadjusted, the SPI was dispersed in water at room temperature beforemixing at elevated temperature.

II. Hydrophilicity as a Function of Mixing and Application Temperaturesof Solutions

Heating a solution of SPI prior to application on a nonwoven has beenshown to improve the performance of the nonwoven on an absorbentproduct. Heating soy proteins causes dissociation of their quaternarystructures, denatures their subunits, and promotes the formation ofprotein aggregates via electrostatic, hydrophobic and disulphideinterchange mechanisms. In addition to heating, the adjustment of pH andionic strength, hydrolysis, and covalent attachment of otherconstituents would be expected to modify the performance of a nonwoventreated with an SPI finish. The hydrophilicity of a nonwoven treatedwith SPI as function of mix temperature, application temperature, andsoy protein solids add-on has been summarized in FIG. 3.

The nonwoven was a 12.5 gsm, hydrophobic (i.e. untreated), polypropyleneSpunbond-Spunbond-Spunbond (SSS) provided by Fitesa, Simpsonville, S.C.Solutions of Clarisoy 100™ were mixed at specified temperatures rangingfrom 22° C. to 80° C. The pH of the SPI solutions was not adjusted inthese experiments. Solution pH values ranged from 2.3 to 2.9. Atemperature of 22° C. was defined as room temperature, although inpractice this could vary from about 15° C. to 30° C. Clarisoy 100™ is anisolated soy protein (ISP) provided by Archer Daniels Midland (ADM,Decatur, Ill.). The nonwoven was finished or treated with solutions ofClarisoy 100™ at specified temperatures ranging from 22° C. to 70° C.using a laboratory-scale padder. Samples were prepared using a two-stagedip-and-nip process to ensure uniform wetting of the nonwoven.

Solutions at the specified concentrations were made in 1500 ml to 3000ml batches with tap water of medium hardness. Clarisoy 100® powder wasslowly added to vigorously-stirred water that was held at the specifiedmixing temperature using a thermocouple-equipped hotplate withtemperature control. After dispersing the powder in the heated water,mixing speed was reduced and maintained for 30 minutes. The solutionbecame clear after 15 to 20 minutes of mixing. About half-way throughthe mixing step, 0.04% n-butanol was added to reduce foaming. Abiobutanol such as Butamax®, which is produced from renewable resources,can optionally be used to reduce foaming. It is not necessary to usebutanol when mixing under less vigorous conditions. Butanol did not havea significant effect on the surface tension of the solution. An 0.04%solution (i.e. 0.0054 M) of n-butanol would reduce the surface tensionof water from a value of 72 mN/m only to about 62 mN/m. After mixing atthe specified temperature, the solution was allowed to cool untilreaching a specified treatment temperature. Samples were treated ±5° C.of a target treatment temperature.

The laboratory padder had two rubber-coated, vertical, 8 in. diameterrolls. Sufficient nip pressure was applied to target a wet pick up onthe nonwoven in the range of 1.0 g. of solution/g. of nonwoven. Each 430mm×430 mm section of nonwoven was immersed in a volume of about 1500 mlof solution at a specified treatment temperature before being calendaredbetween the padder rolls. A two-stage dip-and-nip process was used totreat the nonwoven. Solution was not absorbed uniformly on thehydrophobic nonwoven after the first dip-and-nip cycle. Immediatelyafter the first cycle, the nonwoven sample was re-immersed in thesolution and calendared or nipped a second time. This two-stagedip-and-nip process produced a uniformly wet nonwoven and helped todistribute the dissolved solid uniformly over the fiber surfaces. Thewet weight of the sample was recorded to determine wet pick-up ofsolution before hanging the sample in an oven at 107° C. for 15 min. todry.

Drop values in FIG. 3 were measured using a 4-Hole Drop Test to providea measure of the hydrophilicity of the treated nonwoven. Solids add-onwas calculated from the solution concentration and the wet pick-up ofsolution on the nonwoven (expressed as g. of solution per g. ofnonwoven). Average wet pick-up was calculated from the wet and dryweights of each of three handsheets as they were treated. The pooledstandard deviation for wet-pick was 0.07 g/g. In the 4-Hole Drop Test aplastic plate with dimensions of 75 mm×75 mm×13 mm with four evenlyspaced holes each of 15 mm diameter was placed on a sample of nonwovenwhich was resting on one piece of Whatman No. 4 filter paper (90 mmdiameter). Using an eye dropper, four drops of tap water were droppedinto one hole from a height equal to the thickness of the plastic plate.A Drop Value of 2, 1, or 0 was assigned according to how quickly thedrop penetrated the nonwoven and was absorbed by the filter paper. ADrop Value of 2 was used to indicate that the liquid was spontaneouslyabsorbed by the nonwoven within five seconds. A Drop Value of 1indicated that the liquid was absorbed when the assembly of filterpaper, nonwoven sample, and plastic plate was softly shaken after fiveseconds. A Drop Value of 0 indicated that the liquid was not absorbed.Average Drop Values were calculated from the average values obtainedfrom each of four holes on four samples of nonwoven for a total of 16measurements.

An untreated, hydrophobic nonwoven had average Drop Values in the rangeof 0 to 0.5. Drop Values of 2.0 were measured for hydrophilic SSS andSpunbond-Meltblown-Spunbond (SMS) nonwoven topsheets that had beentreated with conventional finishes. An average Drop Value of greaterthan about 1.2 provided adequate hydrophilicity for liquid acquisitionin an absorbent product. Drop Values less than 1.2 are shaded in FIG. 3.FIG. 3 shows that average Drop Values greater than 1.2 were achieved forsolids add-on greater than 0.5% (or 0.005 g. of solids per g. ofnonwoven) when the solution mixing temperature was equal to or greaterthan about 50° C. to 70° C. Drop Values were not affected by theapplication temperature of the solution, i.e. Drop Values greater than1.2 were achieved when a nonwoven was treated with a solution at ambienttemperature, or about 22° C., as long as that solution was mixed at atemperature equal to or greater than 50° C. The pooled standarddeviation for the average Drop Values was 0.9.

III. Wettability of Prototype Nonwovens Using Gravimetric Absorbent TestSystem

Samples were produced for testing on a Gravimetric Absorbency TestSystem (GATS) to characterize the absorption of saline by the nonwovenover successive absorption cycles. The GATS test was used to assess thedurability of the finish to multiple doses of saline solution. Aftereach test, the nonwoven was removed from the apparatus and rinsed byimmersion in 100 ml of 0.9% saline solution at room temperature for 1minute, then blotted dry with a paper towel. The sample was immediatelyretested after each rinse. FIG. 4 shows the weight (g) of salineabsorbed by three layers of nonwoven as a function of the square root oftime (sec^(0.5)). The liquid was absorbed through a single aperture withthe nonwoven sample supported by a finned plate. The finned platereduced the amount of spurious liquid that could be absorbed between thenonwoven sample and the plate. Results in FIG. 4 were obtained using acommercial 12.5 gsm spunbond nonwoven that had been treated with acommercially-available, proprietary, semi-durable finish.

As shown in FIG. 4, liquid was absorbed more slowly after each of thefour rinses. This was the expected result for wetting of a nonwoven thathad a semi-durable finish. Note, however, that the induction time forabsorption increased after each of the first three rinses while theactual rate of absorption after the induction period remained fairlyconstant. The induction time for wetting after the fourth rinse was verylong, greater than 300 sec, and the rate of absorption after the onsetof wetting much decreased.

As shown in FIG. 5, a nonwoven with an SPI add on of 0.006 g. SPI/g.nonwoven showed much different behavior in this test. This nonwoven wasfinished on a pilot line described in Section V below. Liquid absorptionof the unrinsed nonwoven with the SPI finish was comparable to that ofthe commercially available nonwoven with a conventional syntheticsurfactant finish. After the first rinse there was a clear increase inthe induction time of wetting and a modest decrease in the rate ofwetting after the induction period, compared to the unrinsed sample.However, in contrast to the nonwoven with the commercially availablesynthetic surfactant finish, liquid absorption, performance of thenonwoven with a synthetic surfactant-free SPI finish improved after boththe second and third rinses. Performance after the third rinse wastypically as good or better than that of an unrinsed sample. This was anunexpected result, but can be explained by a finish that was extremelydurable and improved as it hydrated during use.

IV. Spreading of SPI Solution within a Nonwoven Using a Calendar Nip

As shown in Section V below, a high-surface-tension saline solution(i.e. synthetic urine) will spread on and be imbibed by a polypropylenenonwoven that has been treated with a hydrophilic finish comprised ofSPI. However, a high-surface-tension SPI solution will not readilyspread on a hydrophobic polypropylene nonwoven. The nonwoven can betreated by immersing it in a solution of SPI and forcibly removingentrained air to ensure intimate contact between solution and nonwovenfibers. Once the solution comes in contact with the hydrophobicpolypropylene fiber of the nonwoven, the protein adsorbs on the fibersurface and renders the nonwoven more hydrophilic, but the proteincannot adsorb to fiber in areas of the nonwoven that solution cannotspread.

Water with a surface tension of 72.8 mN/m does not spread on alow-surface-energy solid like polypropylene. Conventional nonwovenfinishes that are in widespread use today are comprised of syntheticsurfactants that lower the surface tension of water to a range of about30-37 mN/m (see Table 1 below). These surfactant solutions of lowsurface tension spread on polypropylene fibers and provide a uniformdistribution of surfactant finish upon drying. A 0.1% solids solution ofSPI had a surface tension of 64 mN/m. This solution will not readilyspread in a polypropylene nonwoven. Classes of materials that can beused to make a synthetic surfactant-free nonwoven finish described inthis invention are hydrophilic, but solutions of these materials do notreduce the surface tension of water below 49 mN/m. These solutions arenot spontaneously imbibed by hydrophobic nonwovens, and require specialprocessing to uniformly distribute the finish throughout the nonwovenstructure.

The surface tensions of solutions of SPI at concentrations in the rangeof 0.4%-1.2% solids were in the range of 49-68 mN/m at 22° C. The meanvalue was 58±9.9 mN/m. At these concentrations the surface tension wasindependent of solution concentration. Surface tension was measuredusing a method of capillary rise. Capillary rise was measured afterraising and lowering the liquid in the capillary and measuring thevalues at equilibrium after 10 min.

TABLE 1 Surface Tensions of Liquids and Solutions Surface Tension Liquid(mN/m) Water 72 SPI solution (0.4%-1.2%) 49-68 0.1% 7B Soy Flour 61Silastol 163 (0.4%-6%) 35-37 Silastol PHP 26 (0.4%) 30 Stantex S6757(0.4%-6%) 31-36 0.1% Triton X-100 33 Isopropyl alcohol 22

The Silastol and Stantex materials in Table 1 are surface finishescomprised of proprietary mixtures of synthetic surfactants that are usedto render polypropylene spunbond nonwoven hydrophilic. Silastol 163 is asilicone-free, anionic finish for the production of durable hydrophilicpolyolefin nonwovens, especially topsheets. Silastol PHP 26 is acationic/amphoteric finish for the production of durable hydrophilicpolyolefin staple and spunbond fibers suitable for topsheet. Stantex S6757 is durable hydrophilic finish for polypropylene spunbond materials,especially for hygienic applications. These surfactants are oftenapplied to nonwoven using solution concentrations in the range of 6%. Atsolids in the range of 0.4%-6%, solutions of these materials had asurface tension in the range of 31-37 mN/m. The low surface tension ofthese solutions promotes wetting of the hydrophobic polypropylenenonwoven and enables the nonwoven to spontaneously imbibe the surfactantsolution.

To achieve spreading and contact between an SPI solution and ahydrophobic nonwoven, the nonwoven was immersed in an SPI solution andcalendared to eliminate entrained air and promote intimate contact, evenfor a short period, between nonwoven fiber and solution. A laboratorycalendar with an adjustable nip was used simulate what could be achievedusing a flooded nip or size press on a commercial production line. Table2 shows how the solution concentration of SPI was increased tocompensate for a reduced wet pick up of solution after calendaring. Acritical nip dimension of about 0.150 (in arbitrary units) was requiredto achieve uniform wetting of the nonwoven in this calendar. There was alarge reduction in wet pick up for calendared nonwoven, but nomeaningful change in wet pick up for small changes in nip dimension nearthe critical value.

TABLE 2 Properties of Certain of Methods of Making the Present SheetsDry Wt. of Solution SPI Add On Nonwoven Concentration Nip Wet Pick Up(g. SPI/ Sample (g. SPI/g. NW) Dimension (g. soln/g. NW) g. NW) 0.080.001 None 6.0 0.006 0.08 0.001 0.200 2.3 0.002 0.08 0.002 None 6.40.013 0.08 0.002 0.200 2.8 0.006 0.08 0.002 0.150 3.0 0.006 0.08 0.0020.125 3.0 0.006 0.08 0.004 0.125 3.0 0.012

Runoff tests were used to assess the ability of a stream of liquid topenetrate a topsheet nonwoven and to be absorbed by an absorbent corebefore the liquid could run over the surface of the topsheet nonwoven tothe end or side of an absorbent article. Two runoff tests were used inthis work. One test utilized a model absorbent core and the other usedabsorbent cores from actual baby diapers. In this section the test withthe model absorbent core, as described in Section X.C below, was used.The other test will be discussed in a later section to evaluate theproperties of nonwoven prototypes that had been made on a pilot line andevaluated on baby diapers.

As shown in FIG. 6, performance of 12-13 gsm spunbond nonwovens finishedwith a synthetic surfactant-free topsheet finish at 0.006 g. SPI/g.nonwoven was compared to that obtained for a commercially availablenonwoven finished with a semi-durable synthetic surfactant. The dataclearly show comparable performance for the synthetic surfactant-freetopsheet finish. There was a modest reduction or improvement in LiquidRunoff for the nonwoven with the surfactant-free finish, even though theliquid travel may have been somewhat greater than that measured for thecommercial nonwoven topsheet with a semi-durable surfactant finish.

V. Synthetic Surfactant-Free Nonwoven Finishes Applied on a Pilot Line

A high-surface-tension aqueous solution of SPI will not readily spreadon a hydrophobic polypropylene nonwoven. In earlier sections it has beenshown that lab prototypes can be prepared successfully by immersing asample in a solution and calendaring it to evenly distribute solutionthroughout the nonwoven. A pilot line with a flooded nip size press atNorth Carolina State University was used to validate this approach.Identification of a process that does not require spontaneous spreadingof the aqueous synthetic surfactant-free solution on the hydrophobic,untreated nonwoven was considered to be important for commercial use ofat least some of the present embodiments. The flooded nip on the pilotline was set up and adjusted to achieve uniform wetting of the web inmachine- and cross-directions. The nonwoven was successfully processedusing a steel on rubber roll configuration where the Durometer Hardnessof the rubber roll had a value of 72. Roll pressure was adjusted untilthe wet pick up of the solution on nonwoven was qualitatively uniform inappearance and touch in both MD and CD directions. Variability in wetpick up was checked by weighing samples that had been cut from the web.After adjustment, wet pick up on nonwoven varied less than 10%. Auniform wet pick up of solution could not be achieved using a harderrubber roll with a Durometer Hardness of 90.

Preparation of SPI solution for pilot line runs was done as closely aspossible to lab protocol described above. SPI powder was mixed withdistilled water (<10 μmho conductivity) in a five gallon pail using ahigh-shear mixer at 6000-7000 rpm for 15 minutes at room temperature.The solution was adjusted from its natural pH of 2.7-3.0 to a pH of8.0±0.2 before being placed in a steam jacketed reservoir on the pilotline. It took about 15 minutes for the solution to reach temperature inthe pilot line. The solution was maintained at a temperature of about90° C. in the reservoir to ensure an application temperature of 80° C.in the flooded nip. Wet pick up of solution on the pilot line was lessthan that achieved using the laboratory calendar. Prototypes made in thelab had a wet pick up of about 3 g. solution/g. nonwoven, but only about1 g. solution/g. nonwoven remained on the nonwoven on the pilot lineafter the roll pressure in the flooded nip had been increased to achieveuniform wetting. Solution concentration was adjusted upward during thepilot line trials to achieve a target add on of SPI in the range of0.006-0.008 g. SPI/g. nonwoven. Steam can rolls were maintained at 110°C. on the pilot line to dry the nonwoven at a line speed of 30feet/minute. Prototypes made on the pilot line are listed in Table 3below.

TABLE 3 Pilot Line Prototypes SPI Add On Prototype Base Solution Conc.Wet Pick Up (g. SPI/ No. Nonwoven (g. SPI/g. soln) (g. soln/g. NW) g.NW) 1 12 gsm SSS 0.0025 1.0 0.003 2 0.0050 1.2 0.006 3 15 gsm SMS 0.00251.1 0.003 4 0.0050 1.0 0.005 5 0.0100 0.8 0.008

As described below, several of these prototypes were incorporated intobaby diapers for testing, and certain characteristics and test resultsare summarized in FIG. 7. The testing methods are described in the“Experimental Methods” section below.

A. Example No. 1

This example shows the lab performance of a leading private label babydiaper (Size 4) reconstructed with a 12 gsm SSS spunbond nonwoventopsheet that had been treated with a synthetic surfactant-free SPIfinish (Prototype No. 2 above, with 0.006 g. SPI/g. nonwoven). Thetopsheet of the commercially available diaper was carefully removed bygentle heating with a forced air hair dryer and replaced with theprototype topsheet. All other materials, including the 60 gsmacquisition/distribution layer used on the commercial diaper remainedthe same. To minimize the effect of diaper reconstruction oninterpretation of test results, especially for runoff tests, thetopsheet of the control or commercial diaper was also removed and thenreplaced in its original position. The topsheet of the commercial diapercomprised a 15 gsm nonwoven.

A diaper containing an unfinished hydrophobic spunbond topsheet wasincluded for reference in FIG. 7. This hydrophobic topsheet generatedpoorer performance in third and fourth dose liquid acquisition time(ACQ3 & ACQ4) and poorer performance in side leakage in this test.Higher side leakage in the ACQ(uistion)/REW(etting) test was related tothe very high runoff volumes exhibited by the hydrophobic nonwoven. Incomparison, performance of the diaper that contained the nonwoventopsheet that had been treated with the synthetic surfactant-free finishwas comparable to that of the diaper containing the original, syntheticsurfactant-finished topsheet. The synthetic surfactant-free, hydrophilicSPI finish had imparted useful properties to the initially hydrophobictopsheet nonwoven. In the Anarewet Test, there was a notable advantagein side leakage for the diaper containing the synthetic surfactant-freetopsheet. Runoff improved after each successive dose for the diaper thatcontained the synthetic surfactant-free topsheet. Mannequin leakage,expressed as absorption before leakage (ABL) was significantly improvedfrom 206 g. to 250 g. for the diaper containing a topsheet nonwoven witha synthetic surfactant-free finish.

B. Example No. 2

This example shows the lab performance of a leading private label babydiaper (Size 4) reconstructed with a 15 gsm SMS nonwoven topsheet thathad been treated with a synthetic surfactant-free SPI finish (0.008 g.SPI/g. nonwoven). The synthetic surfactant-free topsheet used with thisdiaper was Prototype No. 5 that was made in the pilot line trialdescribed above. The topsheet of the commercially available diaper wascarefully removed by gentle heating with a forced air hair dryer andreplaced with the prototype topsheet. All other materials, including the60 gsm acquisition/distribution layer used on the commercial diaperremained the same. To minimize the effect of diaper reconstruction oninterpretation of test results, especially for runoff tests, thetopsheet of the reference diaper was also removed and then replaced inits original position.

A diaper containing an unfinished hydrophobic SMS topsheet was includedfor reference in FIG. 7. The diaper containing the SMS topsheet with thesynthetic surfactant-free finish showed comparable performance to thecommercially available diaper, but provided a significant advantage inside leakage in the Anarewet Test. Runoff also improved after eachsuccessive dose for the diaper that contained the syntheticsurfactant-free topsheet. The synthetic surfactant-free SPI treatmenthad imparted an effective hydrophilic finish to the topsheet nonwoven.

Further optimization of the performance of topsheet andacquisition/distribution layer (ADL) nonwovens finished with SPI, aswell as other materials, can proceed using solution concentration,solution pH, solution mixing temperature, nonwoven treatmenttemperature, calendaring to promote liquid spreading, and dryingtemperature. The invention can be extended to include other hydrophilic,but non-surface active, materials. Examples of these will be discussedin a later section.

VI. Additional Examples

Examples 3-6 show liquid acquisition and rewet performance of diapersthat had been reconstructed with topsheet nonwoven that had beenfinished using a laboratory padder as described in the earlier section“Hydrophilicity as a Function of Mixing and Application Temperatures ofSolutions.” A reconstructed diaper is a machine-made diaper that has hadits original topsheet nonwoven dissected and replaced with testmaterial. Control diapers for this experiment had the original topsheetalso dissected and replaced to reproduce any differences in liquidcommunication within the diaper that may have been introduced by thereconstruction process. Size Large diapers from a leading private labelproducer were used to evaluate the topsheets. The absorbent core of thediaper was comprised of 45% fluff and 55% SAP. There was about 11.5 g.of SAP in the absorbent core of the diaper. A partial core length, 50gsm through-air-bonded acquisition layer was used between the topsheetand the core. Examples 3-6 provide results from the Liquid Acquisitionand Rewet (ACQ/REW) Test for diapers reconstructed with SSS topsheetnonwovens that had been finished using various combinations of solutionconcentrations of SPI, types of SPI, SPI add-on levels, solution mixingtemperatures, and solution application temperatures. The pH of the SPIsolutions used to make these samples was not adjusted. Their natural pHwas in the range of 2.2-2.9. The Drop Values for the topsheet nonwovensused in these examples ranged from 1.4-2.0. Example 7 provides acomprehensive assessment of a machine-made diaper that had been producedwith a machine-made SSS topsheet nonwoven finished with SPI.

The SPI-finished topsheet nonwoven in Example 3 (1.2% Clarisoy® 100solution mixed at 80° C. and applied at 22° C.), as indicated in Table4, as evaluated in a lab-reconstructed diaper. Results of testing ofExample 3 are shown in FIG. 8.

TABLE 4 Properties of Example 3 Clarisoy 100 ® SPI Add-On Solution (gsolids/g Mix Application Concentration nonwoven × TemperatureTemperature 4-Hole (%) 100%) (° C.) (° C.) Drop Value 1.2% 2.0% 80° C.22° C. 2.0

Example 4 included a lab-made SPI-finished nonwoven evaluated in alab-reconstructed diaper (1.2% Clarisoy® 150 solution mixed at 80° C.and applied at 22° C.), as indicated in Table 5. Results of testing ofExample 4 are shown in FIG. 9.

TABLE 5 Properties of Example 4 Clarisoy 150 ® SPI Add-On Solution (gsolids/g Mix Application Concentration nonwoven × TemperatureTemperature 4-Hole (%) 100%) (° C.) (° C.) Drop Value 1.2% 2.0% 80° C.22° C. 2.0

Example 5 included a lab-made SPI-finished nonwoven evaluated in alab-reconstructed diaper (0.8% Clarisoy® 100 solution mixed at 80° C.and applied at 50° C.), as indicated in Table 6. Results of testing ofExample 5 are shown in FIG. 10.

TABLE 6 Properties of Example 5 Clarisoy 100 ® SPI Add-On Solution (gsolids/g Mix Application Concentration nonwoven × TemperatureTemperature 4-Hole (%) 100%) (° C.) (° C.) Drop Value 0.8% 1.1% 80° C.50° C. 2.0

Example 6 included a lab-made SPI-finished nonwoven evaluated in alab-reconstructed diaper (0.8% Clarisoy® 100 solution mixed at 50° C.and applied at 22° C.), as indicated in Table 7. Results of testing ofExample 6 are shown in FIG. 11.

TABLE 7 Properties of Example 6 Clarisoy 100 ® SPI Add-On Solution (gsolids/g Mix Application Concentration nonwoven × TemperatureTemperature 4-Hole (%) 100%) (° C.) (° C.) Drop Value 0.8% 0.7% 50° C.22° C. 1.4

Examples 3-6 show that the SPI-treated nonwovens are suitable for use inan absorbent product and can provide a meaningful improvement in SurfaceWetness over a conventional nonwoven finished with synthetic surfactant.Saline was maintained at 22° C. for tests in Examples 3-6. Overall, thediapers containing the SPI-treated nonwovens had somewhat lower (i.e.better) liquid acquisition times and higher (i.e. poorer) rewet valuesafter the first dose. This behavior is consistent with SPI providing amore durable hydrophilic finish than synthetic surfactant. Syntheticsurfactant used in the conventional finish is washed from the nonwovenin use, and the nonwoven becomes less hydrophilic after each dose. Thisresults in higher acquisition times and lower rewet on subsequent dosesof liquid compared to the performance of the diaper made with theSPI-treated nonwoven. The reduction in liquid acquisition times fordiapers with the SPI-treated nonwoven topsheets were not statisticallysignificant at p=0.05, but consistent and directional with p valuesgenerally less than 0.20. There were meaningful reductions in SurfaceWetness for diapers made with the SPI-treated nonwoven topsheets. Forexample, after the fourth dose, Surface Wetness for the diapers with theSPI-treated topsheets ranged from 0.000-0.027 g. compared to a value of0.050 g. for the diaper with the conventional topsheet. Surface Wetnessis a measure of small amounts of saline that can remain trapped betweena wearer's skin and the nonwoven on the surface of the product. It isimportant because synthetic surfactant from a nondurable nonwoven finishcan dissolve in urine and contact skin. The presence of syntheticsurfactant on skin may be associated with skin irritation and transienterythema, as well as an increase in the permeability of the skin to anyirritant that may be present. Side leakage for diapers with theSPI-treated topsheets was less than for diapers with the conventional,synthetic surfactant-treated topsheet.

Example 7 included a machine-made SPI-treated nonwoven evaluated in amachine-made diaper (solution mixed at 80° C. and applied at 65° C.), asindicated in Table 8. Results of testing of Example 7 are shown in FIG.12.

TABLE 8 Properties of Example 7 Clarisoy 100® SPI Add-On Solution (gsolids/g Mix Application Concentration nonwoven × TemperatureTemperature 4-Hole (%) 100%) (° C.) (° C.) Drop Value 1.4% 0.6% 80° C.65° C. 2.0

A commercial-scale textile finishing line at TSG Finishing (Hickory,N.C.) was used to produce 5,000 lineal meters of a SPI-treated nonwovenfor making prototype diapers on a commercial-scale converting machine.The base nonwoven was a hydrophobic (i.e. unfinished), 12.5 gsm FitesaSSS spunbond nonwoven. The padder process was modified to finish thetopsheet using a two-stage dip and nip process at 50 yd./min. with asolution of Clarisoy 100 maintained at 60°-70° C. The solution wasprepared at 1.2 wt. % of Clarisoy® 100 and 0.04 wt. % of n-butanol,however due to evaporative losses during the trial run, the averagesolution concentration was about 1.4%. Tap water was heated to atemperature of 80° C. before adding the Clarisoy 100 and mixing for 30min. The solution was used at its natural pH in the range of 2.2-2.9.Solids add-on calculated from wet pick-up of solution on the nonwovenwas 0.006 g. solids per g. of nonwoven. The nonwoven was dried on atenter frame in an air impingement oven at 225° F. Rolls of theSPI-treated nonwoven were used to make infant diapers on acommercial-scale converting machine at Domtar Personal Care in Delaware,Ohio. Size Large diapers used for this evaluation were made with a 45%fluff/55% superabsorbent polymer (SAP) absorbent core comprised of 11.5g. of SAP. A 50 gsm acquisition/distribution layer (Shalag Nonwovens,Oxford, N.C.) of through-air-bonded synthetic fiber was placed in thediaper between the absorbent core and topsheet. Diapers were made withboth a conventional 13.5 gsm SMS topsheet nonwoven and at 12.5 gsmSPI-treated topsheet nonwoven, and were evaluated using 4-Hole Drop,Conventional Liquid Acquisition/Rewet, Anarewet Liquid Acquisition,Liquid Runoff, and Mannequin Leakage Tests.

This SPI-treated topsheet nonwoven was uniformly wettable and suitablefor use as a topsheet nonwoven in an absorbent product. Drop valuesobtained using the 4-Hole Drop Test were 2.0±0.01 for SPI-treatednonwoven produced both at the beginning and at the end of the trial run.

Values of Liquid Acquisition and Rewet for diapers made with aconventional nonwoven topsheet and the SPI-treated topsheet weregenerally comparable (FIG. 12). Tests were run using saline solutions at22° C. and 37° C. There were statistically significant (i.e., p<0.05)improvements in liquid acquisition times at 22° C. for all doses for thediaper made with the SPI-treated nonwoven. At 37° C., due to highervariability in the acquisition times, there was only a directionalimprovement in fourth dose acquisition time with p=0.14. There weredirectionally poor Rewet values after the third and fourth doses for theSPI-treated nonwoven. These increases in Rewet were small and notstatistically significant. As noted in earlier testing, Surface Wetnessand Side Leakage were better for the diaper made with the SPI-treatedtopsheet.

Similarly, there were directional indications of improved AnarewetLiquid Acquisition times at both 22° C. and 37° C. for the SPI-treatednonwoven that were not statistically significant (FIG. 13). The rate ofliquid acquisition in the Anarewet Test depends more on demandabsorbency than it does in a conventional ACQ/REW liquid acquisitiontest. Acquisition rate in the Anarewet Test would be expected to be moresensitive to the hydrophilicity and durability of the topsheet finish.For saline solutions at 22° C., there were: statistically significant(p<0.05) reductions in Liquid Acquisition time at all doses for thediaper with the SPI-treated nonwoven, directionally higher Rewet afterthe 4th dose for the diaper with the SPI-treated nonwoven but notstatistically significant (p=0.152), comparable surface wetness, andhigher side leakage for the diaper with conventional topsheet. Forsaline solutions at 37° C., there were: no statistically significantdifferences in Liquid Acquisition time, directionally lower 4th doseLiquid Acquisition time for diaper with the SPI-treated nonwoven(p=0.138), directionally higher Rewet after 4th dose for the diaper withthe SPI-treated nonwoven but not statistically significant (p=0.402),comparable Surface Wetness, and higher Side Leakage for the diaper withconventional topsheet.

Liquid Run-Off performance for the diaper containing the SPI-treatednonwoven was significantly better than that of the control diaper thatcontained the conventional nonwoven (FIG. 14). The saline in the LiquidRun-Off Test was adjusted to a surface tension of 60 mN/m with isopropylalcohol and maintained at 37° C. After the first dose, there was ameaningful reduction in Run-Off for the diapers containing theSPI-treated nonwoven. Reductions in liquid run-off and liquidacquisition time over multiple doses are the result of a more durablehydrophilic nonwoven finish imparted by the SPI treatment.

Reductions in liquid run-off would be expected to reduce urine leakagein absorbent products. Evidence of reduced urine leakage has beendemonstrated in an Infant Mannequin Leakage Test. There was astatistically significant (p=0.015) increase (i.e. improvement) inAbsorption Before Leakage (ABL) of the infant diapers made with theSPI-treated nonwoven. ABL values of 226 g. and 200 g. were obtained forthe diapers with the SPI-treated and conventional nonwoven topsheets,respectively. ABL for an absorbent product can generally be increased byincreasing core capacity, as well as by improving containment related toproduct design and fit, however it was an unexpected result of thisinvention to measure a 13% increase in ABL with use of an SPI-treatedtopsheet nonwoven alone.

VII. Preservatives for SPI Solutions

Soy protein can provide nutrients for yeast and bacterial growth whensufficient moisture is present. There is little concern for microbialgrowth on an SFT-finished nonwoven under normal conditions of storageand use. When aqueous solutions of soy protein are prepared and storedprior to manufacture of an SFT nonwoven it may be necessary to add apreservative to the solution to provide adequate shelf life. Peraceticacid can be used to sterilize the solution, and conventionalpreservatives such as sulfites, benzoic acid and sodium benzoates can beeffective. Preservatives such as ascorbic acid, sorbic acid, Natamycin,taurine, aspartame, nisin, polyhexamethylene biguanide hydrochloride,and elemental silver may also be effective. It is important to assurethat the preservative does not impair the hydrophilicity or durabilityof the SFT nonwoven finish. Plantservative WSr (BioOrganic Concepts,Santa Fe Springs, Calif.), derived from Japanese honeysuckle, andNutrabiol T30 WD (Food Ingredient Solutions LLC, Teterboro, N.J.), atocopherol derivative, maintain 4-Hole Drop values >1.2 for nonwovenswith SPI add-on in the range of 0.02-0.020 g. SPI/g. of nonwoven whenthe preservatives are incorporated into the SPI finish such that theratio of preservative to SPI does not exceed a value of about 0.08 to 1,or the preservative amounts to no more than about 8% of SPI on thenonwoven.

VIII. Other Hydrophilic, Non-Surface Active Materials for NonwovenFinishes

A. Examples of Other Soy Materials

Pro-Fam 974 is another soy protein isolate. Arcon S and Arcon SM are soyprotein concentrates with better water dispersibility than soy proteinisolates. 7B Soy Flour, Bakers Soy Flour, and Bakers Soy Flour aredefatted soy flours. In addition to these materials produced by ADM,Cargill Incorporated produces Prolia defatted soy flours.

Solutions of other soy materials were made using 0.001 g. powder/g.solution and mixed at 80° C. for 60 minutes. All of these materials weremore easily dispersed in water than Clarisoy 100. No pH adjustments weremade. The pH of the solutions are shown in FIG. 15. Hydrophobic spunbondwas treated by immersion in the solution at 80° C. for 30 seconds anddried in an oven at 120° C. A drop test discussed in a previous sectionwas used to assess the hydrophilicity of the treated nonwovens, resultsof which are shown in FIG. 15. As indicated, all of the nonwovenstreated with the soy materials performed as well as the commerciallyavailable topsheet made with a semi-durable surfactant finish. There wassome evidence after a warm tap water rinse that these syntheticsurfactant-free soy-finishes were more durable than the commercialsurfactant finish. The good performance of these other soy materialssuggests that many other natural and synthetic materials may fall withinthe teaching of this invention.

B. Hydrolyzed Proteins and Gelatin

Various plant- and animal-derived biopolymers may provide additionalexamples for the present finishes. For example, hydrolyzed collagen,hydrolyzed albumen, hydrolyzed barley protein, hydrolyzed casein,hydrolyzed cottonseed protein, hydrolyzed gelatin, hydrolyzed hemp seedprotein, hydrolyzed whey protein, casein, hydrolyzed silk, glutelinproteins, silk sericin, gum arabic, bovine serum albumin, and variousvegetable proteins. Of particular interest are the Peazazz® pea proteinand Supertein® canola protein isolates produced by Burcon NutraScienceCorporation and zein produced by Flo Chemical Corporation.

C. Polyvinylpyrrolidone (PVP)

PVP is a water-soluble, nonionic polymer that adheres to a variety ofsubstrates. BASF (Kollidon®), Harke Group and International SpecialtyProducts (ISP) produce PVP polymers in several viscosity grades, rangingfrom low to high molecular weight. PVP is mainly used as a binder in wetgranulation and hair spray products. Copolymers of vinyl pyrrolidone andvinyl acetate are also commercially available. PVP will crosslink in airat 150° C. and become insoluble in water. Crosslinking would impartexceptional durability to a nonwoven finish comprised of PVP. Theseproperties suggest that PVP would function particularly well as ahydrophilic nonwoven finish, as well as an inert scaffold for theincorporation of microsilver or skin wellness ingredients.

D. Other Hydrophilic Polymers

Hydrophilic, water-soluble polymers like carboxymethyl cellulose (andother cellulosic polymer derivatives), starches, polyvinyl alcohol, andpolyethylene and polypropylene glycols for providing less durablenonwoven finishes. Many polysaccharides may also provide examples ofthis invention.

IX. Durable, Synthetic Surfactant-Free Finishes as Carrier for SkinWellness Ingredients

The durable, synthetic surfactant-free finishes described in thisinvention can also be used as a carrier or scaffold for incorporation ofskin wellness ingredients in a nonwoven finish for application inabsorbent products. The durability of the finish can be adjusted toaccommodate the desired rate of delivery of any particular activeingredient to wet skin. Examples of skin wellness ingredients includeanti-infective agents such as microsilver, silver sulfadiazine, povidoneiodine, and PVP-stabilized peroxides; anti-viral agents such as citricacid, copper oxide, and Zn salts; and, various skin-rejuvenationingredients widely used in the cosmetic industry. Asynthetic-surfactant-free SPI finish provides a novel, skin-friendlyvehicle for incorporating biopolymers such as 2-methacryloyloxyethylphosphorylcholine (MPC) and its derivatives into a nonwoven finish toimpart bioinert properties and form a hydration shell of water aroundnonwoven fibers.

X. Experimental Methods

A. Liquid Acquisition and Rewet (ACQ/REW)

A conventional liquid acquisition and rewet test was performed accordingto the following procedure. The liquid acquisition is the time inseconds for a section of core to absorb a known volume (usually 75 or100 ml) of 0.9% saline through a 48 mm diameter dosing head. Productswere equilibrated overnight and tested in a room maintained at 22° C.and 50% relative humidity (RH). The saline solution was used at a roomtemperature of 22° C. The dosing head was weighted and had a screen onone end to apply an even pressure of 0.5 pounds per square inch (psi) tothe core at the point of liquid dosing. The remainder of the core wasrestrained under a 150 mm×300 mm plate that weighed 600 g. The dosinghead extended through a hole drilled through the core restraining plateand was positioned over the center of the acquisition layer used on theabsorbent core. A 75 ml dose was metered to the dosing head at a rate ofapproximately 20 ml/sec and the time to absorb the liquid was recordedas the acquisition time (±0.1 sec). After 30 minutes of equilibration,the restraining plate was removed, and a stack of ten filter papers(Whatman 4, 70 mm) were placed on the dosing area under a cylindricalbrass weight of 60 mm diameter. The weight applied a pressure of 0.8psi. After two minutes the weight was removed and rewet was determinedfrom a difference in weight between the wet and dry filter papers (±0.01g). The acquisition and rewet test was repeated for 4 doses.

Surface Wetness and Side Leakage were also determined in this test.Surface Wetness was determined when the restraining plate was removedfrom the core. A paper towel was used to collect liquid still attachedto the plate after the plate had been removed from the core. A singlepaper towel was used to remove liquid from three to five plates used forreplicate samples. The mass of the liquid from the plates was determinedfrom a difference in weight between the wet and dry paper towel (±0.01g.). An average Surface Wetness for each replicate was determined bydividing the total mass of liquid collected from the plates by thenumber of replicates. The steps were repeated for four doses of 75 ml ofliquid.

Side leakage tests were also performed in conjunction with the LiquidAcquisition and Rewet testing. Side leakage can occur by liquid runningoff of the surface of the core, as well as by moving through the coreitself and leaking from the side. In this test, a disposable absorbentbed pad was cut to a width that was 50 mm wider (i.e., 25 mm on eachside) than the diaper and placed under the diaper at the beginning ofthe test. This mat was used to contain any test liquid that was notabsorbed by the diaper core during the test. At the end of the test, thebed pad material was re-weighed to determine the amount of leakage thatoccurred during the test. Values of Side Leakage obtained for eachreplicate were combined to provide an average value of Side Leakage forthe test.

B. ANAREWET Test

The Anarewet test was used to find acquisition times for productswithout forming a hydrostatic head over the dosing area. In particular,the Anarewet apparatus doses the liquid only when a product being testedcan absorb it. A 75 ml dose of 0.9% saline solution at 22° C. wasapplied to the product at a pressure of 20 millibars (mb) and theacquisition or absorption time (without hydrostatic head) was measured.

C. Runoff Test Procedure for FIG. 6

This runoff test simulates the washing/rinsing off (or lack thereof) ofsurfactants or other nonwoven treatments which often occurs undersubsequent insults of saline solution over the top of, or through, anonwoven top-sheet. This run-off test was performed with an absorbentcore and topsheet that were secured on a plexiglass plate that wasinclined 20° above horizontal such that the liquid would flow laterallyacross the surface of the product. A tray was positioned under the lowerend of the sample to collect runoff. Six 75 ml doses of 0.9% saline at22° C. were then applied at 420 ml/min at 5 minute intervals from a tubewith its end disposed 1 cm above the core and dispensing liquid at anangle parallel to the incline of the product in a direction from thefront toward the back of the product. For each dose, the saline thatimmediately ran off the topsheet (not leaking from the core over time)was collected in the tray and the change in weight measured.

D. Runoff Test Procedure for FIG. 14

This run-off test was performed with whole diapers. Diapers were securedon a plexiglass plate that was inclined 33° above horizontal, andoriented such that liquid from a nozzle would flow under gravity fromthe front to the back of the diaper. A nozzle was centered over theacquisition layer in the diaper in a vertical orientation 1 cm from thesurface of the diaper. For each dose, the volumetric liquid flow ratewas held constant at 420 ml/min for respective doses of 35, 70, and 105ml. The diameter of the nozzle orifice was selected to provide a maximumliquid stream velocity of 200 cm/sec at a flow rate of 1200 ml/min. Thetest liquid was a 0.9% saline solution that had its surface tensionreduced to 60 mN/m (at 22° C.) with isopropanol. The solution was heatedsuch that the temperature of the solution at the nozzle exit was 35° C.After each dose, liquid that was not absorbed by the diaper core wascollected at the base of the incline. Two additional doses at the samedose volume were administered at an interval of two minutes. Run-off wasdetermined as a function of dose volume using dose volumes of 35, 70,and 105 ml per dose.

E. Mannequin Testing

For the mannequin testing, Large Size 4 diapers were constructed toinclude topsheets according to the present embodiments. These diaperswere tested on a Size 4 prone Courtray mannequin diaper testercommercially available from SGS Courtray EURL, Douai, France, using theCourtray absorption before leakage (ABL) protocol provided with theapparatus.

The mannequin is made of a soft silicone rubber and has appropriatedimensions for a Large Size 4 infant. In this test a diaper was fittedto the mannequin and stressed until leakage with multiple doses of 0.9%saline test liquid supplied by Lab Chem Inc., Cat. No. 07933, which hada specification of 0.9% Wt./Vol.±0.005% sodium chloride. Products wereequilibrated overnight and tested in a room maintained at 22° C. and 50%relative humidity. The saline solution used was at a room temperature of22° C. Absorption Before Leakage (ABL) was defined as the mass of liquidthat the diaper absorbed (±0.01 g) under conditions of the test before aleak occurred. Higher values of ABL=(Final Weight of Diaper afterLeakage)−(Initial Dry Weight of Diaper) are preferred. The mannequin wasprovided with female and male dosing tubes. The male mode was used inall tests. The liquid was pumped to the mannequin at a rate of 7 ml/secusing a Masterflex L/S Digital Drive, Model No. HV-07523-80 and aMasterflex L/S Easy-Load II Pump Head, Model No. EW-77200-62. Themannequin was placed on a rectangular foam pad that had a waterproofcover. Leakage was detected visually on a sheet of tissue placed underthe mannequin. Times were measured using a stopwatch ±1 sec.

General instructions for fitting a diaper on the mannequin follow. Thediaper should be folded in the longitudinal direction forming a pouch,concave inward, between the legs of the mannequin. The standing gathersof the product need to come to rise while applying it to the mannequin,paying close attention to how they lie in the groin. Correct position isachieved when the standing gathers remain extended and surround the maleadapter evenly. The outer leg elastics are folded outwardly in thecrotch region so that the inner face of the product remains in contactwith the skin of the mannequin. The tabs of the diaper are unfolded andput on smoothly. The diaper is spread flatly on front and backside toensure an even fit. The diaper is then fixed in place with the tapetabs. The tabs should be centered on the landing zone. On a Size 4 Largediaper the ends of the tabs should nearly touch (1 mm±0.5 mm) in themiddle of the landing zone. The front and back ends of the diaper shouldremain at equal height on the torso of the mannequin. Small adjustmentscan be made to align the front and back ends of the diaper, ifnecessary. Differences in diaper dimensions can affect the tightness offit of the diaper around the waist of the mannequin. In the testingdescribed below, folded multi-layer cores were tested incommercially-available diaper chassis.

The protocol for liquid dosing of the product is given in the tablebelow. An initial dose of 75 ml of liquid was delivered at t=0 with themannequin lying on its belly. At t=4 min. the mannequin was turned onits back. At t=5 min. a dose of 25 ml was delivered with the mannequinlying on its back. At t=9 min. the mannequin was turned onto its belly,rotating the torso in the same direction as turned initially. At t=10min. a dose of 75 ml was delivered with the mannequin lying on itsbelly. The mannequin remained on its belly for the remainder of the testand was dosed with 25 ml every 2 min. (e.g., t=12, 14, 16 min., etc.)until leakage occurred. Saline solution that leaks out of the diaperwill be absorbed and spread by the tissue layer that covers the pad andwill present a visible dark spot. After a leak occurred, the diaper wasremoved and weighed. The difference between the wet and initial dryweights of the diaper was defined as Absorption Before Leakage (ABL).

Time (min) Position Dose No. Dose Vol. (ml) 0 Belly 1 75 4 Back — — 5Back 2 25 9 Belly — — 10 Belly 3 75 After 10 min. the mannequin remainson its belly and is dosed with 25 ml every 2 min. until a leak occurs.

The diaper chassis used for making diapers containing the presenttopsheets was a commercially available, private label disposable diaper.The diapers were placed on the Courtray mannequin and the ABL wasmeasured and recorded per the procedure supplied by the manufacturer ofthe mannequin.

From the foregoing, it will be observed that numerous modifications andvariations can be effected without departing from the true spirit andscope of the novel concept of the present invention. It is to beunderstood that no limitation with respect to the specific embodimentsdisclosed herein is intended or should be inferred. The disclosure isintended to cover, by the appended claims, all such modifications asfall within the scope of the claims.

The invention claimed is:
 1. A hydrophilic, synthetic sheet comprising:a sheet of synthetic material having a first surface; where the sheetcomprises a hydrophilic finish including molecules of a water-solubleprotein, where the water-soluble protein comprises a thermally denaturedprotein, dispersed on the first surface; and where the finish issubstantially free of synthetic surfactants, and where a 0.4-10% aqueoussolution of the water-soluble protein has a surface tension greater than50 milliNewtons per meter (mN/m).
 2. The sheet of claim 1, where thefinish does not include synthetic materials capable of reducing thesurface tension of water below 50 milliNewtons/m (mN/m).
 3. The sheet ofclaim 1, where the sheet comprises a nonwoven fabric or a film.
 4. Thesheet of claim 1, where the sheet is a topsheet of an absorbent article.5. The sheet of claim 1, where the sheet is a distribution-acquisitionlayer of an absorbent article.
 6. The sheet of claim 1, where a 0.4-1.2%aqueous solution of the water-soluble protein has a surface tensiongreater than 50 milliNewtons per meter (mN/m).
 7. The sheet of claim 1,where a 1.2-10% aqueous solution of the water-soluble protein has asurface tension greater than 50 milliNewtons per meter (mN/m).
 8. Thesheet of claim 1, where at least 0.004 grams of the molecules of thewater-soluble protein are dispersed on the sheet for each gram of sheet.9. A method of imparting hydrophilic properties to a sheet of polymericmaterial, the method comprising: applying a 0.4-10% aqueous solution ofa water-soluble protein has a surface tension greater than 50milliNewtons per meter (mN/m) to a sheet of polymeric material in anaqueous solution; and drying the sheet such that at least a portion ofthe protein is retained on a surface of the sheet; where the aqueoussolution is substantially free of synthetic surfactants and where thewater-soluble protein comprises a thermally denatured protein.
 10. Themethod of claim 9, where the sheet comprises a nonwoven fabric or afilm.
 11. The method of claim 9, further comprising, prior to applyingthe aqueous solution to the sheet: admixing the water-soluble protein inwater; heating the water to a temperature of between 40° Celsius (C) and99° C.; and stirring the admixture to dissolve the protein in the water.12. The method of claim 11, where the water is heated before admixingthe water-soluble protein.
 13. The method of claim 11, where thetemperature of the water is maintained between 40° C. and 99° C. duringat least a portion of the stirring.
 14. The method of claim 12, wherethe temperature of the water is maintained between 40° C. and 99° C. fora period of time sufficient to thermally denature at least a portion ofthe protein.
 15. The method of claim 11, further comprising: adjustingthe pH of the admixture of water and protein prior to heating thetemperature of the admixture.
 16. The method of claim 9, where thetemperature of the solution is between 20° C. and 40° C. during at leasta portion of applying the aqueous solution to the sheet.
 17. The methodof claim 9, where applying the aqueous solution to the sheet comprises:immersing the sheet a first time in the solution; and immersing thesheet a second time in the solution.
 18. The method of claim 17, furthercomprising: calendaring the sheet between immersing the sheet the firsttime and immersing the sheet the second time.
 19. The method of claim 9,where applying the aqueous solution to the sheet is performed with atleast one coating apparatus selected from the group consisting of: aslot die, a knife coater, a kiss coater, a gravure printer, amultiple-roller coating apparatus, and a screen coating apparatus. 20.The method of claim 9, where the aqueous solution comprises apreservative.
 21. The method claim 20, where the preservative comprisesone or more preservatives selected from the group consisting of:Plantservative, MicroSilver, and Nutrabiol.
 22. The method of claim 9,where the protein comprises soy protein isolate (SPI).